FOSL1 Expression Research Articles

Interaction of NF-κB and FOSL1 drives glioma stemness

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor; GBM’s inevitable recurrence suggests that glioblastoma stem cells (GSC) allow these tumors to persist. Our previous work showed that FOSL1, transactivated by the STAT3 gene, functions as a tumorigenic gene in glioma pathogenesis and acts as a diagnostic marker and potential drug target in glioma patients. Accumulating evidence shows that STAT3 and NF-κB cooperate to promote the development and progression of various cancers. The link between STAT3 and NF-κB suggests that NF-κB can also transcriptionally regulate FOSL1 and contribute to gliomagenesis. To investigate downstream molecules of FOSL1, we analyzed the transcriptome after overexpressing FOSL1 in a PDX-L14 line characterized by deficient FOSL1 expression. We then conducted immunohistochemical staining for FOSL1 and NF-κB p65 using rabbit polyclonal anti-FOSL1 and NF-κB p65 in glioma tissue microarrays (TMA) derived from 141 glioma patients and 15 healthy individuals. Next, mutants of the human FOSL1 promoter, featuring mutations in essential binding sites for NF-κB were generated using a Q5 site-directed mutagenesis kit. Subsequently, we examined luciferase activity in glioma cells and compared it to the wild-type FOSL1 promoter. Then, we explored the mutual regulation between NF-κB signaling and FOSL1 by modulating the expression of NF-κB or FOSL1. Subsequently, we assessed the activity of FOSL1 and NF-κB. To understand the role of FOSL1 in cell growth and stemness, we conducted a CCK-8 assay and cell cycle analysis, assessing apoptosis and GSC markers, ALDH1, and CD133 under varying FOSL1 expression conditions. Transcriptome analyses of downstream molecules of FOSL1 show that NF-κB signaling pathway is regulated by FOSL1. NF-κB p65 protein expression correlates to the expression of FOSL1 in glioma patients, and both are associated with glioma grades. NF-κB is a crucial transcription factor activating the FOSL1 promoter in glioma cells. Mutual regulation between NF-κB and FOSL1 contributes to glioma tumorigenesis and stemness through promoting G1/S transition and inhibiting apoptosis. Therefore, the FOSL1 molecular pathway is functionally connected to NF-κB activation, enhances stemness, and is indicative that FOSL1 may potentially be a novel GBM drug target.

Epigenomic signatures of sarcomatoid differentiation to guide the treatment of renal cell carcinoma

Renal cell carcinoma with sarcomatoid differentiation (sRCC) is associated with poor survival and a heightened response to immune checkpoint inhibitors (ICIs). Two major barriers to improving outcomes for sRCC are the limited understanding of its gene regulatory programs and the low diagnostic yield of tumor biopsies due to spatial heterogeneity. Herein, we characterized the epigenomic landscape of sRCC by profiling 107 epigenomic libraries from tissue and plasma samples from 50 patients with RCC and healthy volunteers. By profiling histone modifications and DNA methylation, we identified highly recurrent epigenomic reprogramming enriched in sRCC. Furthermore, CRISPRa experiments implicated the transcription factor FOSL1 in activating sRCC-associated gene regulatory programs, and FOSL1 expression was associated with the response to ICIs in RCC in two randomized clinical trials. Finally, we established a blood-based diagnostic approach using detectable sRCC epigenomic signatures in patient plasma, providing a framework for discovering epigenomic correlates of tumor histology via liquid biopsy.

FOSL1's Oncogene Roles in Glioma/Glioma Stem Cells and Tumorigenesis: A Comprehensive Review.

This review specifically examines the important function of the oncoprotein FOSL1 in the dimeric AP-1 transcription factor, which consists of FOS-related components. FOSL1 is identified as a crucial controller of invasion and metastatic dissemination, making it a potential target for therapeutic treatment in cancer patients. The review offers a thorough examination of the regulatory systems that govern the influence exerted on FOSL1. These include a range of changes that occur throughout the process of transcription and after the translation of proteins. We have discovered that several non-coding RNAs, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), play a significant role in regulating FOSL1 expression by directly interacting with its mRNA transcripts. Moreover, an investigation into the functional aspects of FOSL1 reveals its involvement in apoptosis, proliferation, and migration. This work involves a comprehensive analysis of the complex signaling pathways that support these diverse activities. Furthermore, particular importance is given to the function of FOSL1 in coordinating the activation of several cytokines, such as TGF-beta, and the commencement of IL-6 and VEGF production in tumor-associated macrophages (TAMs) that migrate into the tumor microenvironment. There is a specific emphasis on evaluating the predictive consequences linked to FOSL1. Insights are now emerging on the developing roles of FOSL1 in relation to the processes that drive resistance and reliance on specific treatment methods. Targeting FOSL1 has a strong inhibitory effect on the formation and spread of specific types of cancers. Despite extensive endeavors, no drugs targeting AP-1 or FOSL1 for cancer treatment have been approved for clinical use. Hence, it is imperative to implement innovative approaches and conduct additional verifications.

TIF1β activates leukemic transcriptional program in HSCs and promotes BCR::ABL1-induced myeloid leukemia.

TIF1β/KAP1/TRIM28, a chromatin modulator, both represses and activates the transcription of genes in normal and malignant cells. Analyses of datasets on leukemia patients revealed that the expression level of TIF1β was increased in patients with chronic myeloid leukemia at the blast crisis and acute myeloid leukemia. We generated a BCR::ABL1 conditional knock-in (KI) mouse model, which developed aggressive myeloid leukemia, and demonstrated that the deletion of the Tif1β gene inhibited the progression of myeloid leukemia and showed longer survival than that in BCR::ABL1 KI mice, suggesting that Tif1β drove the progression of BCR::ABL1-induced leukemia. In addition, the deletion of Tif1β sensitized BCR::ABL1 KI leukemic cells to dasatinib. The deletion of Tif1β decreased the expression levels of TIF1β-target genes and chromatin accessibility peaks enriched with the Fosl1-binding motif in BCR::ABL1 KI stem cells. TIF1β directly bound to the promoters of proliferation genes, such as FOSL1, in human BCR::ABL1 cells, in which TIF1β and FOSL1 bound to adjacent regions of chromatin. Since the expression of Fosl1 was critical for the enhanced growth of BCR::ABL1 KI cells, Tif1β and Fosl1 interacted to activate the leukemic transcriptional program in and cellular function of BCR::ABL1 KI stem cells and drove the progression of myeloid leukemia.

Abstract 5388: FOSL1 promotes glioma tumorigenesis and stemness through NF-κB and STAT3 pathways

Abstract Background: Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor, GBM’s inevitable recurrence suggests that glioblastoma stem cells (GSC) render these tumors persistent. Our previous work showed that FOSL1, which is transactivated by the STAT3 gene, functions as a tumorigenic gene in glioma pathogenesis and is a diagnostic marker and potential drug target for glioma patients. Accumulating evidence shows that STAT3 and NF-κB cooperate to promote the development and progression of various cancers. The link between STAT3 and NF-κB suggests that NF-κB can also transcriptionally regulate FOSL1 and contribute to gliomagenesis. Methods: 1). To investigate downstream molecules of FOSL1, we analyzed the transcriptome after overexpression of FOSL1 in a PDX-L14 line, characterized by very low FOSL1 expression 2). We conducted immunohistochemical staining for FOSL1 and p65 using rabbit polyclonal anti-FOSL1 and p65 in glioma tissue microarrays (TMA) derived from 76 glioma patients and 10 normal individuals. 3). Mutants of the human FOSL1 promoter, featuring mutations in essential binding sites for NF-κB and STAT3, were generated using a Q5 site-directed mutagenesis kit. Subsequently, we examined luciferase activity in glioma cells and compared it to the wild-type FOSL1 promoter. 4). We explore the mutual regulation between NF-κB signaling and FOSL1 by modulating the expression of NF-κB or FOSL1. Subsequently, we assessed the activity of FOSL1 and NF-κB. 5) To understand the role of FOSL1 in cell growth and stemness, we conducted a CCK-8 assay, cell cycle analysis, assessing apoptosis and GSC markers, ALDH1 and CD133 under varying FOSL1 expression conditions. Results: 1) Transcriptome analyses of downstream molecules of FOSL1 show that NF-κB signaling pathways are regulated by FOSL1. 2) p65 protein expression correlates to the expression of FOSL1 in glioma patients. 3) NF-κB is a crucial transcription factor activating the FOSL1 promoter in glioma cells. 4) Mutual regulation between NF-κB and FOSL1 contributes to glioma tumorigenesis and stemness through promoting G1/S transition and inhibition of apoptosis. Conclusion: The FOSL1 molecular pathway is functionally connected to NF-κB and STAT3 activation, enhances stemness, and FOSL1 is a novel GBM drug target. Citation Format: Mingli Liu, Vanajothi Ramar, Azam Khedri, BreAnna Hudson, Shanchun Guo. FOSL1 promotes glioma tumorigenesis and stemness through NF-κB and STAT3 pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5388.

Abstract 6522: Epigenetic modulation decreases myeloid suppression to improve response to immune checkpoint inhibition in breast cancer

Abstract Immune checkpoint inhibitors (ICIs) promote a durable anti-tumor immune response. Unfortunately, many patients with breast cancer are thought to be intrinsically resistant. One potential mechanism of resistance is a myeloid suppressed tumor microenvironment (TME). Targeting myeloid suppression is under investigation as a therapeutic strategy to sensitize tumors to ICI. In our trial, NCI-9844, we demonstrated that the combination of the epigenetic modulator, entinostat with ICIs—nivolumab (anti-PD-1) + ipilimumab (anti-CTLA-4), leads to a 25% objective response rate in patients with advanced breast cancer. Work in our preclinical models showed entinostat decreases suppressive function by myeloid derived suppressor cells (MDSCs). We hypothesized that entinostat decreases intra-tumoral MDSC suppression via the STAT3/AP-1 axis and drives cellular shifts within the TME to improve response to ICI. Here, we examined expression of upstream, downstream, and interacting factors within the STAT3 pathway in MDSCs treated with entinostat. Macro-dissected lung metastases from entinostat treated NeuN mice revealed differential gene expression of AP-1 subunits JunB and FOSL1 in MDSCs identified by single cell RNA sequencing (scRNAseq). Western blot of isolated intratumoral MDSCs from lung metastases revealed decreased STAT3 phosphorylation upon entinostat treatment. In an entinostat treated MDSC-like cell line, J774M, JunB phosphorylation and FOSL1 were both decreased. scRNAseq also revealed decreased gene expression of STAT3 upstream receptors IL4RA and IFNGR1 and increased expression of STAT3 negative regulator SOCS3. Chromatin immunoprecipitation sequencing is planned to further narrow the molecular mechanism of action. Cell-cell communication analysis of scRNAseq data was performed to evaluate the contribution of entinostat treated macrophages, dendritic cells (DCs), and natural killer (NK) cells on MDSC function. We observed increased frequency of DC populations (classic DC2s and Ccr7 DCs). Following combined treatment with entinostat + ICIs, we also found increased DC to T cell signaling strength for receptor-ligand pairs involved in T cell activation, including Tnfsf9__Tnfrsf9, Cd70_Cd27, H2-dmb2_Cd4, and Cd80_Cd28. Analysis of macrophage-T cell interactions revealed a synergistic decrease in signaling associated with immunosuppression after combined treatment, such as Cd80_Ctla4, Tnf_Tnfrsf1b, and Entpd1_Adora2a. Suppressive function of treated sub-populations of macrophages is planned to determine functional effect of findings. Finally, we are using imaging mass cytometry and bulk RNA sequencing to evaluate proposed mechanisms in patient specimens (NCI-9844). The goal of this work is to identify the molecular and cellular mechanisms driving myeloid suppression of the TME thereby identifying potential therapeutic targets. Citation Format: Aaron G. Baugh, Edgar Gonzalez, Jesse Kreger, Yingtong Liu, Batul Al-Zubeidy, Ludmila Danilova, Sarah M. Shin, Valerie H. Narumi, Sofi Castanon, Julie Jang, Elana J. Fertig, Ashley Cimino-Mathews, Elizabeth M. Jaffee, Vered Stearns, Roisin M. Connolly, Won Jin Ho, Adam MacLean, Evanthia T. Roussos Torres. Epigenetic modulation decreases myeloid suppression to improve response to immune checkpoint inhibition in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6522.

Casein Kinase II Inhibitor Sensitizes the Anti-Tumor Effect of EZH2 Inhibitor By Suppressing FOSL1 Expression in Acute Myeloid Leukemia

Background More effective combination therapy is emerging needed owing to the high mortality and poor outcome in acute myeloid leukemia (AML). The genomic amplification and overexpression of Enhancer of zeste homolog 2 (EZH2) occur in AML patients, and high expression of the Casein kinase 2 (CK2) is associated with poor survival in AML patients. Both EZH2 inhibitor and CK2 inhibitors are reported to inhibit cell proliferation and induce apoptosis in AML, however, the anti-leukemia effect of EZH2 inhibitor in combination with CK2 inhibitor has not been reported. The present study aims to investigate the effect of the combination of the EZH2 inhibitor DZNeP with CK2 inhibitor CX4945 in AML and possible underlying mechanisms. Methods A total of 40 newly diagnosed AML patients and 40 bone marrow control from healthy donors were obtained from our institute with the approval of the Ethics Committee. Cell Counting Kit-8 assay (CCK8), Cell cycle assay, and apoptosis assays were applied in THP-1 AML cells treated with control, DZNeP, CX4945, and CX4945+DZNeP. Global transcriptome analysis by RNA-seq was performed in U937 cells treated with 2μM DZNeP; 12.5μM CX4945 or vehicle for 48 hours. FOSL1 mRNA level was examined by qPCR; R2 genomics analysis and visualization application were used for comparison of the expression difference and the Kaplan-Meier overall survival analysis was conducted by the Gene Expression Profiling Interactive Analysis (GEPIA) platform. Results DZNeP only has little effect on cell proliferation arrest in THP-1 cells, but it significantly sensitized the effect of CX4945, and CalcuSyn analysis showed the synergistic effect of the CX4945+DZNeP (Fig.1A). The treatment of CX4945+DZNeP combination induced the G0/G1 phase arrest in THP-1 cells versus single-drug control (Fig. 1B). The combination also significantly increased the % of the apoptotic cells in THP-1 cells as well as the AML-5b primary cells from the patient compared to single-drug controls (p<0.0001) (Fig.1C). These data indicate the synergistic anti-tumor effect of CX4945+DZNep combination in AML. To understand the molecular mechanism underlying the synergy, the global transcriptome was identified in U937 cells. The significantly different expression genes (DEGs) were identified upon CX4945 treatment (∣log2FC∣>1.5, FDR<0.05), or DZNeP treatment (∣log2FC∣>1.0, FDR<0.05) versus vehicle-control; and 1908 overlapped DEGs are identified upon either drug treatment, in which 596 were intersected (429 genes changed in the same direction but 167 changed in the opposite (Fig. 1D). KEGG enrichment analyses showed the overlapped DEGs upon the drug treatment mainly involved in cell cycle, DNA replication, and MAPK signaling pathway. (Fig.1E). It is worth noting that FOSL1 is dramatically downregulated in U937 cells upon treatment of either DZNeP or CX4945 (Fig1.D); and qPCR data showed that the mRNA level of FOSL1 is significantly downregulated by CX4945+DZNeP, DZNeP or CX4945 compared to the vehicle control (p<0.0001) in THP-1 cells (Fig. 1F). These data indicated that the combination exerts its anti-tumor effect by down-regulation of FOSL1 expression in AML. FOSL1 is a key component of the AP-1 transcriptional complex, and overexpression of FOSL1 is associated with invasion, migration, proliferation, and stemness in human solid cancers. We also examined the FOSL1 mRNA level in 40 newly diagnosed patients with AML versus 40 normal bone marrow controls. Results showed the mRNA level of FOSL1 is significantly higher in AML patients than that of normal controls (p<0.001) (Fig1.G). Metadata analysis showed that FOSL1 high expression is associated with short overall survival (p=0.033) (Fig.1H). These results not only suggested the oncogenic role of FOSL1 in AML but also further supported the CX4945+DZNeP combination-induced anti-tumor effect mediated by suppressing FOSL1 expression in AML. The mechanism model is summarized in Fig. 1E. Conclusion The combination of EZH2 inhibitor DZNeP and CK2 inhibitor CX4945 exerts a potent synergistic effect on proliferation arrest, cell cycle arrest, and apoptosis in AML by suppressing FOSL1 expression. Our results reveal the oncogenic role of FOSL1 in AML. Our data also provide experimental hints for the potential clinical trial of the novel combination in AML patients.

DDDR-20. FOSL1 INDUCES TMZ-CHEMORESISTANCE IN GLIOBLASTOMA VIA REGULATION OF IL-6-STAT3TYR705PATHWAY-MEDIATED STEMNESS

Abstract Glioblastoma (GBM) is the most lethal brain tumors with intensive resistance to drug. Although glioblastoma has been tried to treat with diverse strategies, drug resistance is still concerning. Finding new therapeutic targets to improve conventional drug sensitivity has remained a major challenge. Here, a novel therapeutic target, FOSL1, to conventional drug resistant patients was established, in which FOSL1 knockdown restores the temozolomide (TMZ) sensitivity via regulation of IL-6-induced stemness characteristic in glioblastoma cells. We show that FOSL1, contributing to poor prognosis of GBM patients, is closely linked chemo-resistant molecular signatures. In glioblastoma cells, FOSL1 knockdown is affect to apoptosis, G0/G1 arrest, tumor migration and expression of stemness hallmark. These alterations were induced by FOSL1-mediated IL-6-pSTAT3Tyr705 activation via MGMT independent manner. Finally, we show that vemurafenib, targeting FOSL1 expression, can be potential therapeutics for TMZ resistant glioblastoma. Taken together, our results demonstrate that FOSL1 facilitates TMZ chemoresistance via regulating IL-6-pSTAT3Tyr705-mediated stemness in GBM cells. FOSL1 can represent a novel therapeutic target to overcome GBM chemoresistance.

TRPM7 transactivates the FOSL1 gene through STAT3 and enhances glioma stemness

IntroductionWe previously reported that TRPM7 regulates glioma cells’ stemness through STAT3. In addition, we demonstrated that FOSL1 is a response gene for TRPM7, and the FOSL1 gene serves as an oncogene to promote glioma proliferation and invasion.MethodsIn the present study, we determined the effects of FOSL1 on glioma stem cell (GSC) markers CD133 and ALDH1 by flow cytometry, and the maintenance of stem cell activity by extreme limiting dilution assays (ELDA). To further gain insight into the mechanism by which TRPM7 activates transcription of the FOSL1 gene to contribute to glioma stemness, we constructed a FOSL1 promoter and its GAS mutants followed by luciferase reporter assays and ChIP-qPCR in a glioma cell line and glioma patient-derived xenoline. We further examined GSC markers ALDH1 and TRPM7 as well as FOSL1 by immunohistochemistry staining (IHC) in brain tissue microarray (TMA) of glioma patients.ResultsWe revealed that FOSL1 knockdown reduces the expression of GSC markers CD133 and ALDH1, and FOSL1 is required to maintain stem cell activity in glioma cells. The experiments also showed that mutations of − 328 to − 336 and − 378 to − 386 GAS elements markedly reduced FOSL1 promoter activity. Constitutively active STAT3 increased while dominant-negative STAT3 decreased FOSL1 promoter activity. Furthermore, overexpression of TRPM7 enhanced while silencing of TRPM7 reduced FOSL1 promoter activity. ChIP-qPCR assays revealed that STAT3, present in nuclear lysates of glioma cells stimulated by constitutively activated STAT3, can bind to two GAS elements, respectively. We demonstrated that deacetylation of FOSL1 at the Lys-116 residue located within its DNA binding domain led to an increase in FOSL1 transcriptional activity. We found that the expression of TRPM7, ALDH1, and FOSL1 protein is associated with grades of malignant glioma, and TRPM7 protein expression correlates to the expression of ALDH1 and FOSL1 in glioma patients.ConclusionsThese combined results demonstrated that TRPM7 induced FOSL1 transcriptional activation, which is mediated by the action of STAT3, a mechanism shown to be important in glioma stemness. These results indicated that FOSL1, similar to GSC markers ALDH1 and TRPM7, is a diagnostic marker and potential drug target for glioma patients.

Epigenomic profiling nominates master transcription factors (TFs) driving sarcomatoid differentiation (SD) of renal cell carcinoma (RCC)

Abstract Background Sarcomatoid differentiation of RCC (sRCC) is associated with poor survival. Recent studies showed marked response of sRCC to immune checkpoint blockade (ICB). While distinctive patterns of gene expression in sRCC have been identified, the gene regulatory programs and TFs that drive SD remain unknown. The aim of this study is to nominate TFs responsible for SD and to investigate their association with the clinical outcomes of patients with RCC. Methods Chromatin immunoprecipitation and sequencing (ChIP-seq) for H3K27ac – a histone modification associated with active regulatory elements – was performed on pathologically reviewed sRCC and non-sRCC samples collected at the Dana-Farber Cancer Institute. Regulatory elements that were differentially active between the two groups were identified based on levels of H3K27ac (Benjamini-Hochberg q<0.01, log-fold change (LFC) threshold=1). Enrichment of specific TF binding motifs at activated regulatory elements in sRCC was assessed using HOMER. Differential gene expression analysis of TFs was performed using DESeq2 on RNA-seq data from TCGA. A Mann-Whitney U test was performed on RNA-seq data from the IMmotion151 and Javelin Renal 101 clinical trials to compare mean expression level of TFs in transcript per million (TPM) in these trials. Patients with non-sRCC enrolled in the IMmotion151 trials were divided into quartiles based on gene expression levels of candidate TFs. Progression-free survival (PFS) was compared between non-sRCC patients stratified by expression quartiles as well as patients with sRCC using a multivariable Cox proportional-hazards model accounting for age and IMDC risk score. To validate these findings, a similar analysis was performed in the Javelin Renal 101 trial. Results We obtained high-quality H3K27ac ChIP-seq profiles for 9 sRCC and 17 non-sRCC samples. We identified 278 candidate regulatory elements with increased H3K27ac levels in sRCC vs. non-sRCC. These regulatory elements were enriched for nucleotide motifs bound by the TFs FOSL1 and E2F7. Differential expression analysis between 48 sRCC vs. 493 non-sRCC samples showed that FOSL1 and E2F7 were significantly upregulated in sRCC vs. non-sRCC (LFC=1.7, q=5e-11; LFC=1.8, q=1.3e-20; resp.). Mean TPMs of FOSL1 and E2F7 were significantly increased in sRCC vs. non-sRCC in IMmotion151 cohort and Javelin Renal 101 (all p<0.001). Among patients who received sunitinib, those with the highest quartile of FOSL1 and E2F7 expression showed significantly shorter PFS in IMmotion151 patients compared to patients with the lowest quartile of expression (HR=1.6, 95%CI=1.3-2.2, p=0.008 & HR=2.6, 95%CI=1.8-3.7, p<0.001; resp.). Furthermore, patients with highest quartile of expression showed similar PFS compared to patients with sRCC (p=0.56 and p=0.64; resp.). These results were validated in the sunitinib arm of the Javelin Renal 101 cohort (Figure). Figure: Kaplan-Meier curves of progression-free survival (PFS) in patients with in the sunitinib arm of Javelin Renal 101 by sarcomatoid differentiation and FOSL1 expression levels. Conclusions This is the first study to characterize the epigenomic landscape of sRCC by integrating ChIP-seq and RNA-seq data. Our findings implicated FOSL1 and E2F7 as transcriptional regulators of SD with prognostic relevance. These TFs seems to be associated with aggressive behavior in non-sRCC as well. Further studies are underway to functionally validate these results.

Abstract A029: Epigenomic profiling nominates master transcription factors (TFs) driving sarcomatoid differentiation of renal cell carcinoma (RCC)

Abstract Introduction Sarcomatoid RCC (sRCC) is associated with poor prognosis. Recent studies showed promising response rates of sRCC to immune checkpoint blockade (ICB). Although distinct patterns of gene expression in sRCC have been reported, the gene regulatory programs that drive SD remain unknown. This study aims to nominate TFs driving SD and to evaluate their impact on the clinical outcomes of patients (pts) with RCC. Methods Chromatin immunoprecipitation and sequencing (ChIP-seq) for H3K27ac was performed on histologically annotated areas of sRCC and non-sRCC fresh frozen tissue samples collected at Dana-Farber Cancer Institute. Regulatory elements that were differentially active between the two groups were identified (cutoff p<0.01, log-fold change (LFC) threshold=1). Enrichment of specific TF binding motifs at activated regulatory elements in sRCC was assessed using HOMER. Differential gene expression analysis of TFs was performed using DESeq2 on RNA-seq data from TCGA (Benjamini-Hochberg q <0.01, LFC threshold=1). An unpaired student’s t-test was performed to compare mean gene expression levels in transcript per million (TPM) on baseline sRCC and non-sRCC tissue samples from the IMmotion151 trial (sunitinib vs. atezolizumab-bevacizumab in metastatic RCC). Pts enrolled in the IMmotion151 trial were divided into quartiles based on gene expression levels of candidate TFs. Progression-free survival (PFS) was compared between the quartiles using a multivariable Cox proportional-hazards model accounting for age and IMDC risk score. The association of TF expression with the objective radiographic response (ORR) was analyzed using a logistic regression model. Results ChIP-seq was performed on 9 sRCC & 17 non-sRCC samples. We identified 278 candidate regulatory elements with increased H3K27ac levels in sRCC vs. non-sRCC that were enriched for nucleotide motifs bound by the TFs FOSL1 and E2F7. Differential expression analysis between 48 sRCC vs. 493 non-sRCC samples showed that FOSL1 & E2F7 were significantly upregulated in sRCC vs. non-sRCC (LFC=1.7, q=5e-11; LFC=1.8, q=1.3e-20; resp.). Mean TPMs of FOSL1 & E2F7 were significantly increased in sRCC vs. non-sRCC in IMmotion151 cohort (2.5 vs. 1.5 TPM for FOSL1, and 2.9 vs. 1.9 TPM for E2F7, all p<0.001). Pts in the highest quartile of FOSL1 and E2F7 expression showed significantly shorter PFS in IMmotion151 pts receiving sunitinib alone (HR=1.6, 95%CI=1.3-2.2, p=0.008 & HR=2.6, 95%CI=1.8-3.7, p<0.001; resp.). We observed similar results even after controlling for the presence of SD. Increased expression of E2F7 was associated with worse ORR in IMmotion151 pts who received sunitinib alone, even after controlling for the presence of SD (OR=0.24±0.4, p<0.001). Conclusion This is the first study to analyze the epigenomic landscape of sRCC by integrating ChIP-seq and RNA-seq data. Our findings implicated FOSL1 & E2F7 as transcriptional regulators of SD with prognostic relevance. Further studies are underway to validate these results. Citation Format: Karl Semaan, Talal El Zarif, Marc Eid, Valisha Shah, Brad Fortunato, Renee Maria Saliby, Amin H. Nassar, Sarah Abou Alaiwi, Ji-Heui Seo, Chris Labaki, Ziad Bakouny, Sayed Matar, Nourhan El Ahmar, Yasmin Nabil Laimon, Gwo-Shu Mary Lee, Mark Pomerantz, Jacob Berchuck, Sabina Signoretti, Eliezer Van Allen, Toni Choueiri, David Braun, Matthew Freedman, Sylvan Baca. Epigenomic profiling nominates master transcription factors (TFs) driving sarcomatoid differentiation of renal cell carcinoma (RCC) [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr A029.

UBAP2 plays a role in bone homeostasis through the regulation of osteoblastogenesis and osteoclastogenesis

Osteoporosis is a condition characterized by decreased bone mineral density (BMD) and reduced bone strength, leading to an increased risk of fractures. Here, to identify novel risk variants for susceptibility to osteoporosis-related traits, an exome-wide association study is performed with 6,485 exonic single nucleotide polymorphisms (SNPs) in 2,666 women of two Korean study cohorts. The rs2781 SNP in UBAP2 gene is suggestively associated with osteoporosis and BMD with p-values of 6.1 × 10−7 (odds ratio = 1.72) and 1.1 × 10−7 in the case-control and quantitative analyzes, respectively. Knockdown of Ubap2 in mouse cells decreases osteoblastogenesis and increases osteoclastogenesis, and knockdown of ubap2 in zebrafish reveals abnormal bone formation. Ubap2 expression is associated with E-cadherin (Cdh1) and Fra1 (Fosl1) expression in the osteclastogenesis-induced monocytes. UBAP2 mRNA levels are significantly reduced in bone marrow, but increased in peripheral blood, from women with osteoporosis compared to controls. UBAP2 protein level is correlated with the blood plasma level of the representative osteoporosis biomarker osteocalcin. These results suggest that UBAP2 has a critical role in bone homeostasis through the regulation of bone remodeling.

YAP promotes AP-1 expression in tubular epithelial cells in the kidney.

Chronic kidney disease (CKD) is a major health problem. Kidney fibrosis is a hallmark and final common pathway of CKD. The Hippo/yes-associated protein (YAP) pathway regulates organ size, inflammation, and tumorigenesis. Our previous study demonstrated tubular YAP activation by tubule-specific double knockout of mammalian STE20-like protein kinase 1/2 (Mst1/2) induced CKD in mice, but the underlying mechanisms remain to be fully elucidated. Activator protein (AP)-1 activation was found to promote tubular atrophy and tubulointerstitial fibrosis. Therefore, we studied whether YAP regulates AP-1 expression in the kidney. We found that expression of various AP-1 components was induced in kidneys subjected to unilateral ureteric obstruction and in Mst1/2 double knockout kidneys, and these inductions were blocked by deletion of Yap in tubular cells, with Fosl1 being most affected compared with other AP-1 genes. Inhibition of Yap also most highly suppressed Fosl1 expression among AP-1 genes in HK-2 and IMCD3 renal tubular cells. YAP bound to the Fosl1 promoter and promoted Fosl1 promoter-luciferase activity. Our results suggest that YAP controls AP-1 expression and that Fosl1 is the primary target of YAP in renal tubular cells.NEW & NOTEWORTHY Yes-associated protein (YAP) activation leads to tubular injury, renal inflammation, and fibrosis, but the underlying mechanisms are not fully understood. We now provide genetic evidence that YAP promotes activator protein-1 expression and that Fosl1 is the primary target of YAP in renal tubular cells.

Jinfeng pills ameliorate premature ovarian insufficiency induced by cyclophosphamide in rats and correlate to modulating IL-17A/IL-6 axis and MEK/ERK signals.

Jinfeng Pill (JFP) is a classical Chinese medicine formula and composed of 9 herbs, including Epimedium brevicornu Maxim (Yinyanghuo), Cervus elaphus Linnaeus (Lurong), Panax ginseng C.A.Mey. (Renshen), Equus asinus (EJiao), Ligustrum lucidum W.T.Aiton (Nvzhenzi), Reynoutria multiflora (Thunb.) Moldenke (Heshouwu), Curculigo orchioides Gaertn (Xianmao), Neolitsea cassia (L.) Kosterm. (Rougui) and Leonurus japonicus Houtt. (Yimucao). The formula is clinically used to regulate menstrual cycle and alleviate polycystic ovarian syndrome due to its capabilities of ovulation induction. It is therefore presumed that JFP could be used for the therapy of premature ovarian insufficiency (POI) but the assumed efficacy has not been fully substantiated in experiment. To evaluate the effectiveness of JFP on cyclophosphamide (CTX)-induced POI and preliminarily explore its potential mechanisms of action. An experimental rat model of POI was established by using CTX induction to assess the efficacy of JFP. The potential targets of action for JFP alleviating POI were predicted by the combination of network pharmacology and transcriptomics and finally validating by RT-qPCR and Western blot. JFP alleviated the damages of ovarian tissue induced by CTX in the rat model of POI via significantly decreasing serum levels of FSH and LH and the ratio of FSH/LH and increasing the levels of E2 and AMH, accompanied with promoting ovarian folliculogenesis and follicle maturity and reversing the depletion of follicle pool. With the analysis of network pharmacology, pathways in cancer, proteoglycans in cancer, PI3K-AKT, TNF and FoxO signaling pathways were predicted to be influenced by JFP. The results of RNA-seq further revealed that IL-17 signaling pathway was the most important pathway regulated by both CTX and JFP, following by transcriptional misregulation in cancer and proteoglycans in cancer. Combining the two analytical methods, JFP likely targeted genes associated with immune regulation, including COX-2, HSP90AA1, FOS, MMP3 and MAPK11 and pathways, including IL-17,Th17cell differentiation and TNF signaling pathway. Finally, JFP was validated to regulate the mRNA expression of FOS, FOSB, FOSL1, MMP3, MMP13 and COX-2 and decrease the release of IL-17A and the protein expression of IL-6 and suppress the phosphorylation of MEK1/2 and ERK1/2 in CTX induced POI rats. Jinfeng Pill is effective to ameliorate the symptoms of POI induced by CTX in the model of rats and its action is likely associated with suppressing IL-17A/IL-6 axis and the activity of MEK1/2-ERK1/2 signaling.

Abstract 5167: Entinostat's modulation of myeloid derived suppressor cells through the STAT3-NFκB-AP-1 axis decreases suppressive signaling

Abstract Metastatic breast cancer remains one of the leading causes of global cancer incidence in women, despite the benefit of immune checkpoint inhibitors (ICIs) in managing various cancers and improving patient quality of life. Metastatic breast cancer is characterized by extensive infiltration of the tumor microenvironment (TME) with immunosuppressive cells, such as myeloid derived suppressor cells (MDSCs), that inhibit anti-tumoral immune cells and prevent effective activation of the adaptive immune system by ICIs. Previously, our group has shown in the breast TME that epigenetic reprogramming of MDSCs by entinostat, a histone deacetylase inhibitor, decreases MDSC immunosuppressive function and enhances response to ICIs, in part mediated by altered signaling within the Signal transducer and activator of transcription 3 (STAT3) and Nuclear factor kappa B (NFκB) axis. Next, we sought to examine the effects of entinostat on MDSC reprogramming in a distant metastatic TME. Using the syngeneic NT2.5LM NeuN mouse model of metastatic breast cancer, we established spontaneous lung metastases and treated with either vehicle or entinostat (5 mg/kg by oral gavage, 5x/week) for 3 weeks. Single cell RNA sequencing (scRNAseq) of macro-dissected lung metastases revealed a large MDSC population, and unsupervised pathways analysis of the MDSC cluster showed differential regulation of the IL6-JAK-STAT3 and TNFα-signaling-via-NFκB pathways upon entinostat treatment. In line with reports of crosstalk among STAT3, NFκB, and AP-1 pathways regulating inflammation in breast cancer, we also found through scRNAseq differential expression of AP-1 subunits JunB and FOSL1 upon entinostat treatment. At the protein level, western blot analysis of isolated intratumoral MDSCs from lung metastases revealed decreased STAT3 phosphorylation upon entinostat treatment. Using J774M cells, an MDSC-like cell line, we found decreased JunB phosphorylation and decreased FOSL1 protein upon entinostat treatment. Furthermore, preliminary evaluation of imaging mass cytometry (IMC) from tumor biopsies in selected patients with metastatic breast cancer treated with entinostat during the clinical trial NCI-9844 confirmed decreased STAT3 phosphorylation in MDSCs. Taken together, we provide new evidence in the metastatic lung TME that implicates a STAT3-NFκB-AP-1 mediated mechanism leading to decreased MDSC suppression. Evaluating this mechanism in MDSCs taken directly from treated lung metastases represents the most biologically relevant mechanistic study to date, and preliminary translation of findings in patients suggests that planned studies will lead to identification of the mechanism driving response. Citation Format: Aaron G. Baugh, Edgar Gonzalez, Valerie H. Narumi, Sofi Castanon, Jesse Kreger, James Leatherman, Won Jin Ho, Ashley Cimino-Mathews, Vered Stearns, Roisin M. Connolly, Elizabeth M. Jaffee, Adam L. MacLean, Evanthia T. Roussos Torres. Entinostat's modulation of myeloid derived suppressor cells through the STAT3-NFκB-AP-1 axis decreases suppressive signaling. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5167.

Fosl1: friend or foe?

Fos-like antigen 1 (Fosl1) is a protein that belongs to the Fos family of transcription factors. Fosl1 has an impact on (i) carcinogenesis, (ii) acute kidney injury, and (iii) fibroblast growth factor expression. Recently, the nephroprotective effect of Fosl1 by the preservation of Klotho expression was recently identified. The identification of a link between Fosl1 and Klotho expression provides an entirely new field of nephroprotection.

Influence of FOSL1 Inhibition on Vascular Calcification and ROS Generation through Ferroptosis via P53-SLC7A11 Axis.

Vascular calcification during aging is highly prevalent in patients with cardiovascular disease; however, there is still no improvement in clarifying the development of vascular calcification. FOSL1 is a transcription regulator belonging to the AP-1 family, which has a unique function in vascular senescence, but its role in vascular calcification needs to be further explored. Primary mouse vascular smooth muscle cells were isolated and used to construct a calcification model in vitro. Seven-week-old male C57BL/6 mice were used to build the vitD3-induced calcification model in vivo. qRT-PCR and western blot were used to verify the expression of FOSL1 and other genes expressed in vascular smooth muscle cells and aortas. The level of calcification was determined by Alizarin Red S (ARS) staining and the calcium content assay. The level of cellular GSH was detected by the GSH assay kit. Here, we report that FOSL1 was up-regulated after high-calcium/phosphate treatment in both the in vivo and in vitro vascular calcification models. Functional studies have shown that the reduction of FOSL1 attenuates ferroptosis and calcification in vascular smooth muscle cells, as indicated by ARS staining, calcium content assay, and western blot. The inhibition of FOSL1 downregulated the expression of bone-related molecules including Msh Homeobox 2 (MSX2) and tumor necrosis factor receptor superfamily, member 11b/osteoprotegerin (OPG), suggesting that FOSL1 promoted osteogenic differentiation of vascular smooth muscle cells. Furthermore, we found that the ferroptosis-inducing drug erastin can significantly accelerate calcification in the aortic ring while Ferrostatin-1 (fer-1), a drug to protect cells from ferroptosis, can alleviate calcification. Further experiments have shown that inhibiting FOSL1 can promote the expression of ferroptosis-related genes and attenuate calcification. Functionally, cellular GSH levels were increased after the reduction of FOSL1. In this study, we observed a significant protective effect when we reduced the expression of FOSL1 during vascular calcification, and this effect might regulate ferroptosis to a great extent.

Effect of CUX1 on the Proliferation of Hu Sheep Dermal Papilla Cells and on the Wnt/β-Catenin Signaling Pathway.

CUT-like homeobox 1 protein (CUX1), also called CUX, CUTL1, and CDP, is a member of the DNA-binding protein homology family. Studies have shown that CUX1 is a transcription factor that plays an important role in the growth and development of hair follicles. The aim of this study was to investigate the effect of CUX1 on the proliferation of Hu sheep dermal papilla cells (DPCs) to reveal the role of CUX1 in hair follicle growth and development. First, the coding sequence (CDS) of CUX1 was amplified by PCR, and then CUX1 was overexpressed and knocked down in DPCs. A Cell Counting Kit-8 (CCK8), 5-ethynyl-2-deoxyuridine (EdU), and cell cycle assays were used to detect the changes in the proliferation and cell cycle of DPCs. Finally, the effects of overexpression and knockdown of CUX1 in DPCs on the expression of WNT10, MMP7, C-JUN, and other key genes in the Wnt/β-catenin signaling pathway were detected by RT-qPCR. The results showed that the 2034-bp CDS of CUX1 was successfully amplified. Overexpression of CUX1 enhanced the proliferative state of DPCs, significantly increased the number of S-phase cells, and decreased the number of G0/G1-phase cells (p < 0.05). CUX1 knockdown had the opposite effects. It was found that the expression of MMP7, CCND1 (both p < 0.05), PPARD, and FOSL1 (both p < 0.01) increased significantly after overexpression of CUX1 in DPCs, while the expression of CTNNB1 (p < 0.05), C-JUN, PPARD, CCND1, and FOSL1 (all p < 0.01) decreased significantly. In conclusion, CUX1 promotes proliferation of DPCs and affects the expression of key genes of the Wnt/β-catenin signaling pathway. The present study provides a theoretical basis to elucidate the mechanism underlying hair follicle development and lambskin curl pattern formation in Hu sheep.

Synovial Fluid Derived from Human Knee Osteoarthritis Increases the Viability of Human Adipose-Derived Stem Cells through Upregulation of FOSL1

Knee osteoarthritis (Knee OA) is an irreversible condition that causes bone deformity and degeneration of the articular cartilage that comprises the joints, resulting in chronic pain and movement disorders. The administration of cultured adipose-derived stem cells (ADSCs) into the knee joint cavity improves the clinical symptoms of Knee OA; however, the effect of synovial fluid (SF) filling the joint cavity on the injected ADSCs remains unclear. In this study, we investigated the effect of adding SF from Knee OA patients to cultured ADSCs prepared for therapeutic use in an environment that mimics the joint cavity. An increase in the viability of ADSCs was observed following the addition of SF. Gene expression profiling of SF-treated ADSCs using DNA microarrays revealed changes in several genes involved in cell survival. Of these genes, we focused on FOSL1, which is involved in the therapeutic effect of ADSCs and the survival and proliferation of cancer stem cells. We confirmed the upregulation of FOSL1 mRNA and protein expression using RT-PCR and western blot analysis, respectively. Next, we knocked down FOSL1 in ADSCs using siRNA and observed a decrease in cell viability, indicating the involvement of FOSL1 in the survival of ADSCs. Interestingly, in the knockdown cells, ADSC viability was also decreased by SF exposure. These results suggest that SF enhances cell viability by upregulating FOSL1 expression in ADSCs. For therapy using cultured ADSCs, the therapeutic effect of ADSCs may be further enhanced if an environment more conducive to the upregulation of FOSL1 expression in ADSCs can be established.

MARS1 mutations linked to familial trigeminal neuralgia via the integrated stress response

BackgroundWhile new genetic analysis methods are widely used in the clinic, few researchers have focused on trigeminal neuralgia (TN) with familial clustering (≥ 2 TN patients in one kindred family). Previous literature suggests that familial trigeminal neuralgia (FTN) may be associated with inherited genetic factors. To date, few next-generation sequencing studies have been reported for FTN. This study investigated the pathogenic mechanism of FTN by using whole-exome sequencing (WES) technology, which may enhance our understanding of human TN pathophysiology. MethodWe performed WES for 7 probands from families of FTN. Sanger sequencing was performed for two control groups (FTN family members group and nonfamilial TN subject group) to potentially identify new FTN-related gene mutations. In families where FTN probands carried potentially pathogenic gene mutations, the ribonucleic acid (RNA) of FTN probands and related family members, as well as nonfamilial TN patients were analysed by RNA sequencing (RNA-seq) to confirm differential gene expression.ResultsSeven probands were derived from 3 Chinese families. WES and Sanger sequencing identified MARS1 mutation c.2398C > A p.(Pro800Thr) in Family 1. MARS1 mutation was confirmed in 14/26 [53.8%] members of Family 1 in FTN family member group, while none of nonfamilial TN subjects had this MARS1 mutation. RNA-seq showed that 3 probands in Family 1 had higher expression of Fosl1 (Fos-like antigen 1) and NFE2 (Nuclear factor, erythroid 2) than 3 subjects in the nonfamilial TN subject group. Fosl1 and NFE2 are genes related to integrated stress response (ISR).ConclusionMARS1 mutations may cause chronic activation of ISR, contribute to ISR pathophysiological changes in FTN, and cause/accelerate peripheral nerve degeneration. The findings of this study can enrich our knowledge of the role of molecular genetics in TN in humans.